If the top and bottom bases of a solid are equal in area, lie in parallel planes, and every section of the solid parallel to the bases is equal in area to that of the base, then the volume of the solid is the product of base and altitude.
Volume Theorem
See also
Cavalieri's Principle, VolumeExplore with Wolfram|Alpha
References
Kern, W. F. and Bland, J. R. "Volume Theorem." §12 in Solid Mensuration with Proofs, 2nd ed. New York: Wiley, pp. 27-28, 1948.Referenced on Wolfram|Alpha
Volume TheoremCite this as:
Weisstein, Eric W. "Volume Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/VolumeTheorem.html